1. Field of the Invention
The present invention relates to a method for manufacturing a circuit board for use in an electronic device, and more particularly to a method for manufacturing a hybrid circuit board which is a multilayer circuit board in which the high-density wiring is required and a plurality of component mounting portions are connected to each other by a flexible cable portion.
2. Description of the Related Art
Although a circuit board has electronic component mounted thereon and is installed in various electronic devices, it is often the case that three-dimensional component mounting is required in order to realize a compact electronic device. Therefore, a technique for folding a circuit board and the like is needed.
In order to realize the three-dimensional component mounting, there is adopted a technique using a circuit board consisting of, e.g., a material which can be folded or using a hybrid circuit board in which electronic components are mounted on a plurality of circuit boards and these circuit boards are connected to each other by a collapsible cable portion.
However, the technique using the circuit board consisting of the above-described collapsible material increases a number of wiring patters to be folded in case of a multilayer circuit board and the like to make it difficult to fold, and there is such a undesirable problem as that connectivity of the through-hole plating and the like is deteriorated by the fold.
On the other hand, in case of the hybrid circuit board for connecting the circuit boards to each other through the collapsible cable portion, a terminal portion must be provided for connecting the cable portion and a space for that portion must be assured. Also, a trouble for connecting soldering and the like is required, which degrades the working property.
It is therefore an object of the present invention to provide a method for manufacturing a hybrid circuit board capable of integrally forming a component mounting portion and a cable portion by previously forming a punched-out opening portion to a circuit board at a part corresponding a collapsible cable portion when manufacturing the hybrid circuit board for connecting a plurality of circuit boards having electronic components mounted thereon to each other through the collapsible cable portion.
To achieve this aim, a method for manufacturing a hybrid circuit board according to the present invention adopts a technique for integrally connecting a plurality of component mounting portions through a collapsible cable portion by constituting a required internal circuit board so as to provide a punched portion in which only a collapsible cable portion for, e.g., a flexible circuit board for connecting a plurality of component mounting portions to each other is exposed, superimposing on at least one side of the internal layer circuit board an external layer board having an opening portion through an adhesive member having each opening formed at a portion corresponding to said cable portion, and thereafter forming a wiring pattern for the component mounting portions to the external layer board to carry out a blank and pierce process of the respective component mounting portions.
Here, a one-sided copper-clad laminate can be used for the external board, and a pre-preg or an interlayer adhesive can be used for the adhesive member. On the other hand, a required through-hole portion can be formed between the internal circuit board and the external board without restraint.